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Old 09-03-2010, 01:01 PM   #1
justin_otherguy
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Default Viewsonic VA1912wb problems

Hello, I am happy I found this place.
I have a Viewsonic VA1912wb that started out with one problem and ended up with another.

It began with a flicker that would go away after the display warmed up. It got gradually worse so that it would flicker constantly, but the colors were good this whole time.

So I surfed around on the net and found that people were replacing bad caps on the power board for this problem. I popped the case open and found 2 caps that were bulging on top. These were twin 220uF 25V caps. I replaced them with ones from Radio Shack. They were 220uF and 35V.

When I powered back on, the flicker was gone but now all the colors look inverted. The picture on the desktop almost appears as a negative image.

So, knowing Radio Shack parts can be crap, I thought maybe it was the new caps. So I ordered more caps from digikey. All panasonic FM series.
I re-replaced the 2 220uF caps, and two related 1000uF caps I thought might help. NO DICE.

There are two other caps I ordered replacement for (2200uF 10V and 1000uF) but have yet to replace. I would like to find out if I am on the right track or if maybe the thing is fried.

The kicker is that the flicker (the original problem) is gone... but I inherited another one in the process.

I tried to be as detailed as possible, and included lots of pics.
TIA for any suggestions.
Attached Images
File Type: jpg signal_1280x960.jpg (250.3 KB, 86 views)
File Type: jpg screen_compare_1280x960.jpg (128.8 KB, 67 views)
File Type: jpg screen_compare2_1280x960.jpg (136.4 KB, 49 views)
File Type: jpg power_front_caps_1280x960.jpg (143.5 KB, 81 views)
File Type: jpg power_front_caps2_1280x960.jpg (153.8 KB, 65 views)
File Type: jpg power_front_1280x960.jpg (169.2 KB, 90 views)
File Type: jpg power_back2_1280x960.jpg (136.9 KB, 54 views)
File Type: jpg power_back_1280x960.jpg (231.4 KB, 50 views)
File Type: jpg both boards_1280x960.jpg (152.3 KB, 66 views)
File Type: jpg screen_compare3_1280x960.jpg (338.6 KB, 71 views)
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Old 09-03-2010, 01:10 PM   #2
smason
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Default Re: Viewsonic VA1912wb problems

I did an LG monitor a few weeks ago, that was completely dead.
I re-capped it and it came back on but the colours were really bad.

Hitting the auto-setup button didn't help.
I accidentally found a white-balance reset in the menus, and pushed it, looks perfect now. I'm not sure if the bad caps corrupted a setting, or what.
I'd definitely browse through the menus, might be a similar problem.
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36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....
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Old 09-03-2010, 01:20 PM   #3
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Default Re: Viewsonic VA1912wb problems

Quote:
Originally Posted by justin_otherguy View Post
I tried to be as detailed as possible, and included lots of pics.
Wow, the internals of this monitor look identical to my non working CMV CT-934D. The only difference is that the Viewsonic has a sound input jack.

PS. Great pics and description.

Hopefully smason's suggestion fixes it. Let us know.
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Old 09-03-2010, 01:40 PM   #4
justin_otherguy
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Default Re: Viewsonic VA1912wb problems

Quote:
Originally Posted by smason View Post
I accidentally found a white-balance reset in the menus, and pushed it, looks perfect now. I'm not sure if the bad caps corrupted a setting, or what.
I'd definitely browse through the menus, might be a similar problem.
I tried that, but to no avail. Found a service manual online and tried to access the white balance menu. I couldn't get it to come up, but now I have something else to read. Will keep looking.
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Old 09-03-2010, 02:54 PM   #5
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Default Re: Viewsonic VA1912wb problems

Nearly the same as Acer 1717 to
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Old 09-03-2010, 03:11 PM   #6
justin_otherguy
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Default Re: Viewsonic VA1912wb problems

Quote:
Originally Posted by justin_otherguy View Post
So, knowing Radio Shack parts can be crap, I thought maybe it was the new caps. So I ordered more caps from digikey. All panasonic FM series.
I re-replaced the 2 220uF caps, and two related 1000uF caps I thought might help. NO DICE.

I just realized I made a mistake... the two smaller "new" caps are 220 uF. I mis-labeled them in the pics as 1000uF... guess it doesn't really matter, just makes for a great "well i'm an idiot" moment.
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Old 09-03-2010, 03:28 PM   #7
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Default Re: Viewsonic VA1912wb problems

Quote:
Originally Posted by justin_otherguy View Post
There are two other caps I ordered replacement for (2200uF 10V and 1000uF) but have yet to replace. I would like to find out if I am on the right track or if maybe the thing is fried.

The kicker is that the flicker (the original problem) is gone... but I inherited another one in the process.


TIA for any suggestions.
1) Since the 2200uf and 1000uf are rated at 10V, I suspect they supply/filter the 5V output, which supplies the video/logic board. If the 5V output is "corrupted" due to these possibly bad caps, then anything is possible.

2) Did you remove the logic board for any reason? If yes, maybe re-seating the two ribbon cables from it to the LCD panel might help.
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Old 09-03-2010, 03:41 PM   #8
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Default Re: Viewsonic VA1912wb problems

Quote:
Originally Posted by jetadm123 View Post
1) Since the 2200uf and 1000uf are rated at 10V, I suspect they supply/filter the 5V output, which supplies the video/logic board. If the 5V output is "corrupted" due to these possibly bad caps, then anything is possible.
On my nearly identical CMV power board, I can confirm those 2 caps listed above are for the 5V output. I traced the back of the caps directly to the 5V ouput.
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Old 09-03-2010, 03:49 PM   #9
justin_otherguy
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Default Re: Viewsonic VA1912wb problems

Quote:
Originally Posted by jetadm123 View Post
1) Since the 2200uf and 1000uf are rated at 10V, I suspect they supply/filter the 5V output, which supplies the video/logic board. If the 5V output is "corrupted" due to these possibly bad caps, then anything is possible.

2) Did you remove the logic board for any reason? If yes, maybe re-seating the two ribbon cables from it to the LCD panel might help.
Perhaps I will go ahead and replace those as well then... not much to lose at this point.
I have not removed the logic board at all. The ribbon cables appear to be well attached. Not sure how to remove them... do they just pull out?
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Old 09-03-2010, 03:55 PM   #10
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Default Re: Viewsonic VA1912wb problems

Quote:
Originally Posted by justin_otherguy View Post
Perhaps I will go ahead and replace those as well then... not much to lose at this point.
I have not removed the logic board at all. The ribbon cables appear to be well attached. Not sure how to remove them... do they just pull out?
I would recap first. If that doesn't work, then look at reseating the cables. The reason is that they are very fragile and the tabs or connectors can break easily.
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Old 09-03-2010, 04:13 PM   #11
seanc
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Default Re: Viewsonic VA1912wb problems

My first thought was a cable possibly being in backwards, but if you haven't unplugged any then it shouldn't be that.
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Old 09-03-2010, 04:16 PM   #12
justin_otherguy
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Default Re: Viewsonic VA1912wb problems

I went ahead and did the two 10V caps and that made no difference. Was kind of expecting that but hoping it would all come back to life.

ETA: Now I dont know if this is a stupid question or not, but when I put the boards back together and plug the monitor into a PC, there's no metal cover or case on the monitor... would that in any way make a difference? I do have the ground screw in the board and one other. Just trying to think if its a dumb mistake I'm making. The color was fine when I started. Just flickering. I looked to see if I saw any cold solder joints, or if I accidentally bridged anything when I was soldering... neither seems to have occurred.

Last edited by justin_otherguy; 09-03-2010 at 04:20 PM.. Reason: edit to add more text
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Old 09-03-2010, 07:31 PM   #13
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Default Re: Viewsonic VA1912wb problems

The cover shouldn't make any difference.
Have you googled to see if there are any service modes you can go into, perhaps there's a master reset in a hidden menu.

I'm still thinking corrupt settings, but I might be out to lunch.
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Old 09-03-2010, 07:33 PM   #14
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Default Re: Viewsonic VA1912wb problems

Also, how are the voltages? In spec?
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Old 09-03-2010, 07:52 PM   #15
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Default Re: Viewsonic VA1912wb problems

I know this sounds trivial, but can you go back and check all the caps you replaced are in the correct orientation? In other words, you didn't solder the "+" lead of the cap to ground and vice versa.
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Old 09-03-2010, 10:26 PM   #16
justin_otherguy
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Default Re: Viewsonic VA1912wb problems

Quote:
Originally Posted by smason View Post
The cover shouldn't make any difference.
Have you googled to see if there are any service modes you can go into, perhaps there's a master reset in a hidden menu.

I'm still thinking corrupt settings, but I might be out to lunch.
I found a service manual, but it hasn't been very useful. I found how to get into the "white balance" menu that I read about in another post somewhere, but I couldn't get that to work. Other than that, it mostly seems to troubleshoot to board level, not component.

Quote:
Originally Posted by smason View Post
Also, how are the voltages? In spec?
To be honest, I don't know what I would be looking for. I have multimeter, are there places I should be looking for "standard" voltages?

Quote:
Originally Posted by jetadm123 View Post
I know this sounds trivial, but can you go back and check all the caps you replaced are in the correct orientation? In other words, you didn't solder the "+" lead of the cap to ground and vice versa.
Yes, time and again. The board is actually very well marked for that. If its something obvious, it is eluding me still.

Thanks for all the suggestions so far...
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Old 09-03-2010, 10:29 PM   #17
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Default Re: Viewsonic VA1912wb problems

Quote:
Originally Posted by justin_otherguy View Post
To be honest, I don't know what I would be looking for. I have multimeter, are there places I should be looking for "standard" voltages?
smason probably means looking for a steady 5V DC on the connector pins between the power board and the logic board.
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Old 09-03-2010, 11:28 PM   #18
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Default Re: Viewsonic VA1912wb problems

Quote:
Originally Posted by retiredcaps View Post
smason probably means looking for a steady 5V DC on the connector pins between the power board and the logic board.
Ah okay. Well, the results are interesting I think. Strange voltages on some of the pins, I think. (see attached pic) I measured twice to be sure.
There was no input signal attached, only power.

Voltages green are at power on when green LED is lit.
Voltages amber are after about 5 sec when the LED switches to amber.
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File Type: jpg bridge_voltages_1280x960.jpg (178.5 KB, 60 views)
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Old 09-03-2010, 11:36 PM   #19
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Default Re: Viewsonic VA1912wb problems

Quote:
Originally Posted by justin_otherguy View Post
Strange voltages on some of the pins, I think.
1 - probably lcd on/off
2 - ground
3 - ground
4 - 5V DC - standard for standby
5 - 12V DC - another secondary voltage
6 - possibly backlight on/off
7 - don't know
8 - don't know

7-8 could be for brightness control?
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Old 09-07-2010, 07:46 AM   #20
justin_otherguy
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Default Re: Viewsonic VA1912wb problems

Maybe this pic will help more. Don't know what I was thinking, but there are two sides to the header and I only measured one. In addition, I didn't realize there were labels printed on the board, so I included the pin labels on the pic too.

I do have a service manual with schematics but I have to admit that most of it is greek to me. I have a little electronic experience, but am very rusty.

Does anyone know if this is even a common problem? I've searched and found a few instances of it, but no solutions yet.
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File Type: jpg bridge_voltage2A.jpg (316.7 KB, 63 views)
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